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Abstract

Tool vibration is a key factor that affects surface finish, generates noise, and reduces the tool life during conventional boring because of the excessive overhanging length of the tool holder. The interaction between the dynamics of the machine tool and the boring process led to progressive vibration. The creation of appropriate mechanisms in reducing tool vibration will help manufacturing industries to become more productive. In this research, in order to control vibration in the overhanging boring bar, a passive vibration control method was employed. Constrained layer dampers consist of boring bar, substrate, and elastic materials and it is used to minimize tool vibration produced during boring operation. The investigation utilized computational analysis through the ANSYS Workbench platform, employing key parameters such as the overhanging length of the tool holder (100, 150, and 200 mm), substrate material (aluminum, brass, and copper), and elastic material (Nitrile rubber, Natural rubber, and polyurethane). A comprehensive series of 27-run boring experiments were conducted to assess the impact of the constrained layer damper on tool vibration and cutting properties. The results of the study revealed remarkable improvements in various performance metrics. The constrained layer damper demonstrated an impressive 98% reduction in tool vibration, signifying its efficacy in dampening vibrational forces during the boring operation. Furthermore, a substantial 83% decrease in surface roughness was observed, indicating enhanced machining precision and surface finish. The constrained layer damper also exhibited a noteworthy 97.5% reduction in tool wear, highlighting its ability to significantly prolong tool life under challenging machining conditions.

Keywords

Constrained layer damper tool vibration boring process surface roughness tool wear

Introduction

Nowadays high quality product with good dimensional accuracy, higher production rate, less tool wear, cost savings, and increase in performance with reduced environmental factor are the challenges dealt by the modern manufacturing industries. According to the hypothesis made by Guillem Quintana et al.¹ during machining, a weak dynamic stiffness tends to cause self-excited vibration, which can be reduced by applying a damping effect. In boring tool, vibration is caused by the dynamic interaction between workpiece and tool. Tool vibration leads to wavering surface on workpiece which results toward modulated chip thickness and increase in cutting force. Sam Paul et al.² reviewed the influence of tool vibration in metal cutting and concluded that tool vibration can produce significant levels of noise, affect surface quality of the product, and generate excessive tool wear. Authors reduced the tool vibration in metal cutting by adding a damper to the tool holder. Various types of dampers have been employed in the past to reduce tool vibration during metal cutting, which includes passive, active, and semi-active. The passive damper offers adequate dampening performance, affordable in comparison to other dampers, is straightforward in construction.³

Regenerative chatter in the boring process can be controlled utilizing passive vibration control techniques including the installation of vibration absorbers using restricted layer dampers. A passive control technique consist of two elastic materials that typically have very low damping material is known as constrained layer viscoelastic layer.^4,5 Regenerative chatter in machining operations was managed using tuned mass dampers, which were constructed from restricted viscoelastic dampers.^6,7 A revolving boring bar made of carbon fiber epoxy composite was created, and experimental tests were utilized to determine the boring bar’s ideal geometry.⁸ To increase chatter stability, a nano composite materials is inserted in boring bar.⁹ A constrained layer damper was created to reduce chatter in end mill cutter during the end milling process.¹⁰ To increase the machining stability of the boring process, a constrained layer damper was added to the boring bar. Constrained layer damper optimization was carried out through beam theory and computational analysis.¹¹ Johnson et al.¹² used computational analysis to determine the damping ratio on three-layer composite bar made of viscoelastic layers. In milling process, thin walled member was subjected to constrained layer damper and the results of the experiments revealed an improvement in surface finish.¹³ Researchers looked at the effect of constrained layer damper in chatter frequency during drilling.¹⁴ Yuhuanet al.¹⁵ used constrained layer damper in boring bar to reduce regenerative chatter by computational method. The stability of chatter during deep hole boring was examined. Constrained layer dampers was utilized to increase a thin boring bar’s resistance to chatter.¹⁶

Recent studies have made significant strides in optimizing cutting parameters for specific materials, with a notable example being the investigation into finishing milling of Hardox 400 steel by F Kura.¹⁷ Their study employed PVD TiAlN+TiN coated carbide inserts, and the experimental design followed a Taguchi L16 orthogonal array. The evaluation criteria were based on the signal/noise (S/N) ratio, providing a comprehensive assessment of the impact of control factors on surface roughness. In a notable contribution to the field, Nas, Engin, and Fuat Kara ¹⁸ conducted machinability tests on a corrosion-resistant superalloy, subjecting it to both shallow and deep cryogenic treatments via EDM. This study underscores the significance of cryogenic treatment types on the processing performance of the material, introducing an experimental design encompassing pulse-on time, peak current, and material types. The research leverages the Taguchi L18 method to optimize parameters, offering a systematic approach to achieving optimal results for average surface roughness (Ra) and material removal rate (MRR). F Kura et al.,¹⁹ represents a notable contribution to the field, emphasizing the impact of different cutting parameters on the performance of CVD and PVD-coated carbide tools. Guvenc et al.,²⁰ proposed a sliding mode-based active vibration control system which was deployed to mitigate chatter during turning processes. In sliding mode control, the acceleration data received from the cutting tool was used as feedback information and the same data was used for identifying the necessary reaction force for the actuator. Also mathematical model was created by taking the highest vibrations in the direction of the plunge axis. Vibrations signals generated during machining were collected, filtered, integrated, and analyzed using Fast Fourier Transform (FFT) technique. From the results they concluded that chatter was controlled with high accuracy and sliding mode controller technique offers a promising and holistic approach in the dynamic nature of the metal cutting process.

Constrained layer damper is a relatively new technology that has gained significant attention in recent years due to its effectiveness in reducing structural vibrations. Constrained layer damper is a damping technique that involves sandwiching a viscoelastic material between two stiff layers of metal or composite materials to form a composite panel and is widely used in the aerospace, automotive, and civil engineering industries. The novelty of constrained layer damper lies in its ability to effectively reduce structural vibrations over a broad range of frequencies. The viscoelastic layer in the composite panel dissipates the mechanical energy of the vibration thereby, effectively reducing the amplitude and the duration of the vibration. Unlike traditional damping techniques such as passive damping and tuned mass dampers, which are only effective at specific frequencies, constrained layer damper is effective over a broad range of frequencies, making it a versatile and highly efficient technique. Another advantage of constrained layer damper is its lightweight and compact design. The sandwiched composite panel can be made to fit any shape or size, making it suitable for a wide range of applications. Moreover, since the constrained layer damper is a passive damping technique, it requires no external power source or maintenance, making it highly cost-effective in the long run. The constrained layer damper is a novel and highly effective damping technique that has gained significant attention in recent years due to its broad frequency range, lightweight and compact design, and cost-effectiveness. Its versatility and efficiency make it an ideal solution for reducing structural vibrations in a wide range of applications. In the recent decade, many researchers have studied the effect of constrained layer damper in engineering applications. However, a research gap was identified in the area of suppression of tool vibration during boring process using constrained layer damper technique. Constrained layer damper was designed and developed by substrate and elastic material in a ring type on boring bar. The study involved designing, developing, and testing of constrained layer damper with varying overhanging length, substrate material, and elastic material to examine the effects of tool wear, surface finish, and tool vibration during boring of hardened AISI4340 steel. The constrained layer damper demonstrated high effectiveness in reducing tool vibration, resulting in notable improvements in both tool life and surface finish during the boring of hardened AISI4340 steel.

In Sect. 2, we described the computational analysis of boring tool with constrained layer damper by varying overhanging length, substrate material, and elastic material. In Sect. 3, we introduced the 27 run experimental analysis by varying overhanging length, substrate material, and elastic material in boring tool. In Sect. 4, the results and discussion section we analyzed experimental analysis and computational analysis results. In Sect. 5, we described the conclusion and outcomes of the research purpose and the advantages of using constrained layer damper.

Computational analysis of boring tool with constrained layer damper—design of constrained layer damper

A ring type constrained layer damper is installed through a hole drilled in tool bar which reduces the rigidity of the boring bar but also increases the natural frequency and deflection of the bar. The reduction in stiffness and mass, where the latter has a significant impact, causes a steady increase in natural frequency and deflection. The addition of constrained layer damper improves damping and makes up for the 10% drop in stiffness.²¹ In this paper, boring bar has a set inner and outer diameter of 15 mm and 30 mm, respectively. With the aforementioned dimensions, the bar was modeled in the ANSYS WORKBENCH software. Tables 1 and 2 list the material characteristics of boring bars and constrained layer damper. Three hollow cylinders are built using ANSYS WORKBENCH, and they are connected to one another with boring bar material as the exterior layer, substrate layer as the middle layer, and elastic material as the interior layer, in that order. The Design of Experiments (DOE) method is used to determine the best geometry for the constrained layer damper to regulate deflection throughout the boring process based on the results of deflection for various substrate layers and elastic materials. To determine the deflection of a boring bar with constrained layer damper, static studies are employed. The cutting force of magnitude 500 N is employed for static analysis.²² Finite element simulations is carried out by varying the overhanging length, substrate material layer, and elastic material layer which is presented in Table 3.

Table 1.

Materials used in constrained layer damper.

Overhanging length (mm)	Substrate material	Elastic material
100	Copper	Nitrile rubber
150	Aluminum	Natural rubber
200	Brass	polyurethane

Table 2.

Properties of tool holder.

Name of the part	Material	Density (kg/m³)	Young’s modulus (MPa)	Poisson’s ratio
Tool Shank	Carbon steel	7850	2.09 × 10⁵	0.3
Insert	Tungsten carbide	15800	5.55 × 10⁵	0.28
Sim	Steel	7850	2.09 × 10⁵	0.29

Table 3.

Properties of constrained layer damper material.

Name of the part	Material	Density (kg/m³)	Young’s modulus (MPa)	Poisson’s ratio
Substrate material	Copper	8942	1.23 × 10⁵	0.34
	Aluminum	2713	0.7 × 10⁵	0.33
	Brass	8267	0.9 × 10⁵	0.345
Elastic material	Nitrile rubber	75	1628	0.4089
	Natural rubber	100	50	0.499
	Polyurethane	1265	1880	0.48

Static analysis was used to calculate the deflection of varying overhanging length of boring tool holders with constrained layer damper and a conventional boring bar. In this work, both elastic and substrate materials were taken into account. With and without a constrained layer damper, a static study for each of the three overhanging lengths of 200, 150, and 100 mm was conducted, and the corresponding maximum deflections were calculated. Table 4 shows the deflections of constrained layer damper constructed of various materials with three overhanging length and a comparison of the deflection for tools with constrained layer damper and a conventional damper. Figures 1(a)–(c) and 2(a)–(c) show the deflection plots for tool holders constructed of substrate material and elastic material at overhanging lengths of 100, 150, and 200 mm, respectively. From Table 5 & Figures 1 (a)–(c) and 2(a)–(c) maximum deflection was measured as 0.1442 mm for tool holders with constrained layer damper positioned at 100 mm overhanging length and as 0.1456 mm for tools without constrained layer damper. Maximum deflection was measured as 0.39693 mm for tool holders with constrained layer damper positioned at 150 mm overhanging length and as 0.4058 mm for tools without constrained layer damper. The deflection of boring bar with and without constrained layer damper was discovered to be 0.92216 and 0.93887 mm, respectively, for 200 mm of overhanging length. From the result, it is found that deflection of the tool reduced effectively when constrained layer damper was used in a boring bar. The constrained layer damper built of copper (a substrate material) and polyurethane (an elastic material) offer better results when compared to other materials, as is evident from the Table 5 and Figures 3–5. The deflection increases as the clamping length decreases.

Table 4.

The deflection of boring tool holder with constrained layer damper.

S.No.	Substrate material	Elastic material	Deflection of constrained layer damperboring tool with varying overhanging length
S.No.	Substrate material	Elastic material	100 mm	150 mm	200 mm
1	Copper	Nitrile rubber	0.14413	0.39694	0.92219
		Natural rubber	0.14414	0.39697	0.92236
		Polyurethane	0.14412	0.39693	0.92216
2	Aluminum	Nitrile rubber	0.14467	0.3992	0.92857
		Natural rubber	0.14469	0.39926	0.92875
		Polyurethane	0.14466	0.39919	0.92855
3	Brass	Nitrile rubber	0.14436	0.39789	0.92488
		Natural rubber	0.14437	0.39795	0.92505
		Polyurethane	0.14435	0.39788	0.92485

Figure 1.

(a) Deflection for 100 mm overhanging length with constrained layer damper. (b) Deflection for 150 mm overhanging length with constrained layer damper. (c) Deflection for 200 mm overhanging length with constrained layer damper.

Figure 2.

(a) Deflection for 100 mm overhanging length without constrained layer damper. (b) Deflection for 150 mm overhanging length without constrained layer damper. (c) Deflection for 200 mm overhanging length without constrained layer damper.

Table 5.

Deflection for constrained layer damper and conventional boring bar.

Overhanging length (mm)	Conventional boring bar (deflection – mm)	Constrained layer damper (deflection - mm) (Substrate material – Copper) (Elastic material – Polyurethane)
100	0.1456	0.14412
150	0.40586	0.39693
200	0.93887	0.92216

Figure 3.

Constrained layer damper on tool vibration (100 mm overhanging length) during boring process.

Figure 4.

Constrained layer damper on tool vibration (150 mm overhanging length) during boring process.

Figure 5.

Constrained layer damper on tool vibration (200 mm overhanging length) during boring process.

Experimental analysis

Three hollow drilling bars with and without constrained layer damper were fabricated to study the effect of constrained layer damper on tool vibration and cutting performance during boring process. In one of the hollow boring bars, the constrained layer damper was press fitted, and machining tests were run. Additionally, it was made sure that all of the boring bars had the same specifications for comparison.

Material and parameters

A boring tool with the specifications S25T PCLNR 12F3 was employed in this study. It had 30 mm diameter and 300 mm length. Workpiece consist of 100 mm outer diameter, 50 mm diameter, 100 mm length, and is manufactured of AISI 4340 steel with a 45 HRC.²³ The construction of a boring bar using a constrained layer damper is shown in Figure 6, and the experimental constrained layer damper setup with input and output parameters is shown in Figure 7. A 200 mm long, 15 mm diameter carbon steel boring tool was drilled using spark machining. In the fabrication process, a hollow drilling bar made of substrate and elastic material was pressed inside which is locked with adjustable screw made of steel. 100 m/min for the cutting speed, 0.06 mm/min for the feed, and 0.5 mm for the depth of cut which optimized. Cutting tests were conducted for 2 min in a dry cutting environment.²⁴

Figure 6.

Constrained layer damper in a boring bar.

Figure 7.

Experimental setup of constrained layer damper.

Design of experiments

To calculate the static deflection with modification in overhanging length, substrate material, and elastic material in computer analysis, design of tests is carried out. In experimental analysis, it is also utilized to quantify tool wear, tool vibration, and surface roughness by altering the overhanging length, substrate material, and elastic material. DOE is carried out using Minitab software, which primarily relies on a statistical foundation. There are a total of 27 experiments, with three levels and three factors.

Analysis of variance

Analysis of variance is utilized to determine input factors effect on machining of the boring process. Analysis of variance is used to determine the important cutting parameters that affect the material’s machinability.²⁵ The total sum of squared deviations, which is used to rank the cutting parameters, is estimated using the equation shown below.

{SS}_{T} = \sum_{i = 1}^{n} {(η_{i} - η_{m})}^{2}

(1)

In this study, 27-run experiment on a Kirloskar lathe was used. Using a piezoelectric vibrometer pickup mounted at the top of the tool holder, the amplitude of tool vibration was measured. In this study, the amplitude of tool vibration in the vertical direction was measured, as the vibration, particularly in the radial direction, is known to have a deleterious effect on the machined surface texture. Using a Kistler type 9257B dynamometer, the measurement of the main cutting force was conducted. In this study, the cutting force acting in the tangential direction (Y-direction), termed as the main cutting force, was considered due to the small magnitudes of feed force and thrust force, making them least harmful and least significant. The measurement of surface roughness was conducted using a Mitutoyo surface roughness tester, specifically the SJ 210 model. In the industry, various simple surface roughness amplitude parameters, including roughness average (Ra), root-mean square roughness (Rq), maximum peak-to-valley roughness (Ry or Rmax), etc., are commonly utilized. The average roughness (Ra) neutralizes the impact of extreme points by averaging all peaks and valleys of the roughness profile, ensuring that a few outlying points have no significant influence on the final results. In this study, “Ra” was chosen to express surface roughness due to its simplicity and effectiveness as a method for monitoring surface texture and ensuring consistency in the measurement of multiple surfaces. Flank wear is created on the relief face of a cutting tool when it rubs against the workpiece. This type of tool wear is caused by an abrasion mechanism and progresses gradually. Impaired accuracy of machined parts is caused by flank wear, as it induces deflection of the cutting tool. The maximum flank wear typically occurs at the extremities of the cutting edge, while in the central zone, the wear land is relatively uniform. According to the ISO standard, the flank wear land width (VBB) served as the criterion for tool life. In this study, the average VBB was measured using a toolmaker’s microscope and taken into consideration. The toolmaker’s microscope has a least count of 0.005 mm. Using a toolmaker’s microscope, chip thickness was measured, and cutting temperature was determined using a noncontact-type pyrometer. The accelerometer has a sampling rate of 2,56,000 Hz, the resolution of surface roughness is 0.02 μm, and the sensitivity for the Kistler dynamometer is approximately ≈–7 pC/N. In order to improve cutting performance, a set of constrained layer damper parameters were developed, including the overhanging length (100, 150, and 200 mm), the substrate material (copper, aluminum, brass), and the elastic material (Nitrile rubber, Natural rubber, and polyurethane). Three levels of constrained layer damper parameters are shown in Table 6 and the experimental data and results from the machining process in Table 7.

Table 6.

Representation of parameters of Constrained Layer Damper.

S. No	Name of the input parameter	Numerical/Categorical value	Representation
1	Overhanging length (mm)	100	M₁
		150	M₂
		200	M₃
2	Substrate material	Copper	T₁
		Aluminum	T₂
		Brass	T₃
3	Elastic material	Nitrile rubber	S₁
		Natural rubber polyurethane	S₂
		Natural rubber polyurethane	S₃

Table 7.

Experimental design and results.

Standard order	Parameters			Tool vibration (mm)	Surface roughness (μm)	Tool wear (mm)
Standard order	Overhanging length (mm)	Substrate material	Elastic material	Tool vibration (mm)	Surface roughness (μm)	Tool wear (mm)
1	M₁	T₁	S₁	0.17413	1.408	0.265
2	M₁	T₁	S₂	0.09414	1.245	0.179
3	M₁	T₁	S₃	0.01412	0.669	0.03
4	M₁	T₂	S₁	0.25467	1.918	0.356
5	M₁	T₂	S₂	0.17469	1.79	0.27
6	M₁	T₂	S₃	0.09466	1.179	0.14
7	M₁	T₃	S₁	0.33435	2.429	0.463
8	M₁	T₃	S₂	0.25437	2.39	0.375
9	M₁	T₃	S₃	0.17435	1.69	0.258
10	M₂	T₁	S₁	0.42994	1.958	0.705
11	M₂	T₁	S₂	0.34997	1.795	0.619
12	M₂	T₁	S₃	0.26993	1.219	0.47
13	M₂	T₂	S₁	0.5122	2.468	0.796
14	M₂	T₂	S₂	0.43226	2.34	0.71
15	M₂	T₂	S₃	0.35219	1.729	0.58
16	M₂	T₃	S₁	0.59089	2.979	0.903
17	M₂	T₃	S₂	0.51095	2.94	0.815
18	M₂	T₃	S₃	0.43088	2.24	0.698
19	M₃	T₁	S₁	0.95719	2.508	1.045
20	M₃	T₁	S₂	0.87736	2.345	0.959
21	M₃	T₁	S₃	0.79716	1.769	0.81
22	M₃	T₂	S₁	1.04357	3.018	1.136
23	M₃	T₂	S₂	0.96375	2.89	1.05
24	M₃	T₂	S₃	0.88355	2.279	0.92
25	M₃	T₃	S₁	1.11988	3.529	1.243
26	M₃	T₃	S₂	1.04005	3.49	1.155
27	M₃	T₃	S₃	0.95985	2.79	1.038

In metal cutting, flank wear, nose wear, and crater wear were considered as influential wear indices in measuring the quality of the finished product. SEM images of flank wear, nose wear, and crater wear for a specimen is shown in Figure 8. Flank wear occurs on the relief face of cutting tool and it is due to the rubbing of cutting tool relief face against the workpiece. This flank wear is caused by abrasion mechanism and progress gradually resulting towards deflection of cutting tool which in turn affects the accuracy of the manufactured product. Nose wear occurs in the nose area of cutting tool which results in catastrophic tool failure. Due to the accuracy factor in measuring nose wear, measurement of nose wear was found to be difficult. Crater wear occurs in the rake face of cutting tool and accompanied by excessive cutting temperature. This rate of diffusion increases exponentially with the rise in temperature. Among these wears, flank wear which is an indication of progressive tool wear and also has an effect on tool vibration, was considered and measured in this study.

Figure 8.

SEM images of flank wear, nose wear, and crater wear.

Result and discussion

Static analysis was employed to calculate the deflection. The study focused on varying overhanging lengths (100 mm, 150 mm, and 200 mm) of boring tool holders. Both elastic and substrate materials were considered in the analysis. The study compared tool holders with constrained layer dampers and conventional boring bars. Separate static studies were conducted for each of the three overhanging lengths. Table 4 provides details on the deflections of constrained layer dampers constructed from various materials. Table 4 presents the maximum deflections for tool holders with and without constrained layer dampers. Figures 1(a)–(c) and 2(a)–(c) illustrate deflection plots for tool holders made of substrate and elastic materials at different overhanging lengths. The maximum deflection was measured at different overhanging lengths, with and without constrained layer dampers. For instance, at 100 mm overhanging length, the deflection was measured as 0.1442 mm for tool holders with constrained layer dampers and 0.1456 mm for tools without dampers. The comparison between boring bars with and without constrained layer dampers. The deflection was measured for a 200 mm overhanging length, showing a reduction in deflection when constrained layer dampers were used. Constrained layer dampers made of copper (substrate material) and polyurethane (elastic material) were identified as providing better results compared to other materials. Table 5 and Figures 3–5 depict the comparative results shows that deflection increases as the clamping length decreases.

ANOVA has been applied to determine the individual interactions of control factors on output parameters.^26,27 The ANOVA results for the output parameters on percentage effects of the parameters for overhanging length, substrate material, and elastic material in the boring cavity on tool vibration are shown in Table 8 and were determined to be 72.06%, 13.74%, and 13.18%, respectively. When compared to substrate material and elastic material, overhanging length greatly reduces tool vibration, according to ANOVA analysis (Table 8). According to Table 9, the overhanging length, substrate type, and elastic material each contributed 41.12%, 37.89%, and 21.85% of the surface roughness, respectively. Table 10 shows that the overhanging length, substrate material, and elastic material parameters have a 66.45%, 16.39%, and 16.11%, respectively, percentage contribution to tool wear. Tool vibration, tool wear, and surface roughness all showed minimal percentages of error during prediction, with respective values of 1.02%, 1.21%, and 1.03%. The overhanging length of the boring tool is the most significant constrained layer damper parameter that affects cutting efficiency and damping capacity, according to the findings of the Analysis of variance study. The Analysis of variance was performed with MINITAB16. As the present work deals with the effect of metallic substrate and rubber elastic materials on tool vibration, statistical analysis was not performed. The overhanging length of the boring tool, along with substrate material, and elastic material, have a significant influence on damping efficiency, according to the Analysis of variance analysis.

Table 8.

ANOVA for tool vibration.

Source	DF	Seq SS	Adj SS	Adj MS	F	p	Contribution%
Overhanging length	2	2.89067	2.89067	1.44533	1059188	0.000	72.06
Substrate material	2	0.11710	0.11710	0.05855	42908	0.000	13.74
Elastic material	2	0.11522	0.11522	0.05761	42218	0.000	13.18
Error	20	0.00003	0.00003	0.0789			1.02
Total	26	3.12302

Table 9.

ANOVA for surface roughness.

Source	DF	Seq SS	Adj SS	Adj MS	F	p	Contribution%
Overhanging length	2	5.4450	5.4450	2.7225	3330.68	0.000	41.12
Substrate material	2	5.0790	5.0790	2.5395	3106.82	0.000	37.89
Elastic material	2	2.8616	2.8616	1.4308	1750.42	0.000	21.85
Error	20	0.0163	0.0163	0.0008			1.12
Total	26	13.4020

Table 10.

ANOVA for tool wear.

Source	DF	Seq SS	Adj SS	Adj MS	F	p	Contribution%
Overhanging length	2	2.75280	2.75280	1.37640	28051	0.000	66.45
Substrate material	2	0.21825	0.21825	0.10913	2224.02	0.000	16.39
Elastic material	2	0.19368	0.19368	0.09684	1973.67	0.000	16.11
Error	20	0.00098	0.00098	0.00005			1.03
Total	26	3.16571

Overhanging length has the highest percentage effect on tool vibration because longer overhanging lengths lead to increased deflection and higher leverage, amplifying vibrations. Shorter overhanging enhances stiffness and reduces vibration. Overhanging length contributes the most to surface roughness because shorter overhanging lengths result in less tool deflection, leading to finer surface finishes. The effect is more pronounced compared to substrate material and elastic material. Overhanging length has the highest percentage contribution to tool wear because longer overhanging lengths increase the likelihood of tool vibration and wear. Shorter lengths minimize these effects, emphasizing their impact on tool wear.

From Figure 9(a), tool vibration is reduced (less than 0.2 mm) at the contact of level 1 of overhanging length (100 mm) and substrate material (copper). But tool vibration is high (more than 1 mm) at level 3 region of overhanging length (200 mm) and substrate material (brass). Similarly in Figure 9(b), tool vibration is reduced (less than 0.2 mm) at the contact of level 3 of overhanging length (100 mm) and elastic material (Polyurethane). But tool vibration is high (more than 1 mm) at level 1 region of overhanging length and elastic material (natural rubber). From Figure 9(c), tool vibration is mediocre (0.2 – 0.4 mm) at level 3 region of substrate material (copper) and elastic material (polyurethane). But tool vibration is very high (above 0.6–0.8 mm) at level 1 region of substrate material (aluminum) and elastic material (natural rubber). The variable overhanging length, substrate material, and elastic material test for tool vibration shown in Figures 9(a)–(c) revealed that when the boring tool holder is with a constrained layer damper made of copper and polyurethane, the tool vibration was significantly reduced.

Figure 9.

(a) Contour plot of Tool vibration versus Substrate material and Overhanging length. (b) Contour plot of Tool vibration versus Elastic material and Overhanging length. (c) Contour plot of Tool vibration versus Substrate material and Elastic material.

Tool vibration is significantly reduced when the overhanging length is at level 1 (100 mm) and the substrate material is copper. Conversely, high tool vibration is observed at level 3 (200 mm) with a substrate material of brass. Shorter overhanging lengths generally result in lower tool vibrations due to reduced leverage and increased stiffness. Copper’s higher damping capacity compared to brass contributes to the lower vibration observed. Lower tool vibration is seen at level 3 (100 mm) with polyurethane, while higher vibrations are observed at level 1 (200 mm) with natural rubber. Polyurethane, being an elastic material with good damping properties, effectively absorbs and dissipates vibrations. In contrast, natural rubber may not offer the same level of damping, leading to higher vibrations. Significantly reduced tool vibration when the constrained layer damper is made of copper and polyurethane. Copper’s damping properties, combined with the damping capabilities of polyurethane, create an effective system for absorbing and minimizing tool vibrations.

From Figure 10(a), surface roughness has significant reduction (1 – 1.5 μm) at the level 1 region of overhanging length (100 mm) and substrate material (copper). But surface roughness is substantial high (3–3.5 μm) at level 3 region of overhanging length (200 mm) and substrate material (aluminum). Similarly Figure 10(b), surface roughness is reduced (1–1.5 μm) at the interaction of level 3 of overhanging length (100 mm) and elastic material (polyurethane). But surface roughness is substantial high (3–3.5 μm) at level 1 region of overhanging length (200 mm) and elastic material (natural rubber). From Figure 10(c), surface roughness has significant reduction (1–1.5 μm) at level 3 region of substrate material (copper) and elastic material (polyurethane).But surface roughness is very high (3–3.5 μm) at level 1 region of substrate material (aluminum) and elastic material (natural rubber). Figures 10(a)–(c) show the results of the variable overhanging length, substrate material, and elastic material test for surface roughness. It was found that when the boring tool holder with a constrained layer damper made of copper and polyurethane, the surface roughness was significantly reduced.

Figure 10.

(a) Contour plot of surface roughness versus Substrate material and Overhanging length. (b) Contour plot of surface roughness versus Elastic material and Overhanging length. (c) Contour plot of surface roughness versus Substrate material and Elastic material.

Substantial reduction in surface roughness at level 1 (100 mm) with copper, while high roughness is observed at level 3 (200 mm) with aluminum. Shorter overhanging lengths reduce vibration, leading to finer surface finishes. Copper, being softer than aluminum, might also contribute to lower tool wear and, consequently, reduced surface roughness. Reduced surface roughness at level 3 (100 mm) with polyurethane, higher roughness at level 1 (200 mm) with natural rubber. Similar to the effect on tool vibration, polyurethane’s damping properties contribute to smoother cutting, while natural rubber may lead to increased tool deflection and surface roughness. Significant reduction in surface roughness when the constrained layer damper is made of copper and polyurethane. The combined damping properties of copper and polyurethane contribute to minimizing tool vibration and, consequently, improving surface finish.

Based on the data presented in Figures 11(a)–(c), we observed notable variations in tool wear under different conditions. In Figure 11(a), it is evident that when the overhanging length was set at level 1 (100 mm) and the substrate material was copper, there was a substantial reduction in tool wear, with measurements consistently below 0.2 mm. Conversely, when the overhanging length increased to level 3 (200 mm) and the substrate material switched to aluminum, tool wear increased significantly, ranging from 1 mm to 1.2 mm. Moving to Figure 11(b), we noted a similar trend. When the overhanging length was at level 3 (100 mm) and the elastic material used was polyurethane, tool wear remained consistently below 0.2 mm. However, when the overhanging length was set to level 1 (200 mm)and natural rubber was employed as the elastic material, tool wear increased substantially, ranging from 1 mm to 1.2 mm. Figure 11(c) provided additional insights. Tool wear was notably reduced (ranging from 0.4 mm to 0.6 mm) when the substrate material was copper and the elastic material was polyurethane at level 3 overhanging length. Conversely, higher tool wear (ranging from 0.8 mm to 1 mm) was observed in most cases when the substrate material was aluminum and the elastic material was natural rubber at level 1. Overall, the analysis of Figures 11(a)–(c) demonstrates that the combination of a copper substrate material and polyurethane as the elastic material led to a significant reduction in tool wear.

Figure 11.

(a) Contour plot of tool wear versus Substrate material and Overhanging length. (b) Contour plot of tool wear versus Elastic material and Overhanging length. (c) Contour plot of tool wear versus Substrate material and Elastic material.

Substantial reduction in tool wear at level 1 (100 mm) with copper, significant increase at level 3 (200 mm) with aluminum. Shorter overhanging lengths reduce tool wear by minimizing deflection. Copper’s softer nature compared to aluminum also contributes to lower wear rates. Consistently low tool wear at level 3 (100 mm) with polyurethane, substantial increase at level 1 (200 mm) with natural rubber. Polyurethane’s damping properties reduce the impact forces on the tool, leading to lower wear. Natural rubber, being less effective in damping, results in higher wear rates. Significant reduction in tool wear when the constrained layer damper is made of copper and polyurethane. The combination of copper and polyurethane effectively dampens vibrations and minimizes wear, prolonging tool life.

Based on the experimental data, Table 11 consist of input parameters for increasing tool life, surface finish and reduced to tool vibration. It was found that for reducing tool vibration and improving cutting efficiency, the overhanging length should be 100 mm, copper should be the substrate material, and polyurethane should be used as the elastic material. Confirmatory experiments were conducted and compared to conventional boring tools using the input parameters of 100 mm of overhanging length, copper as the substrate material, and polyurethane as the elastic material. Tool vibration was reduced by 98%, surface finish was enhanced by 97.5%, and tool wear was decreased by 83% for the tool equipped with constrained layer damper, according to the confirmatory experimental results in Table 12. Table 13 compares analytical and experimental findings for tool vibration with and without constrained layer damper. It is evident from computational and experimental data that using a constrained layer damper when boring hardened AISI4340 steel significantly reduces tool vibration, yet the outcomes were marginally different. The overhanging length of the constrained layer damper boring tool appears to have a significant impact on damping capabilities based on computational and experimental results. The overhanging positions used in this experiment were 100, 150, and 200 mm, and it can be inferred from the data that the overhanging length at 100 mm from the tool edge offers greater resistance to tool vibration than the positions at 150 and 200 mm, respectively. When the overhanging length is between 150 and 200 mm, the damping force will provide an unbalanced effect, and when paired with the main cutting force, this causes significant vibration and lowers cutting effectiveness. This demonstrates that when the constrained layer damper boring tool is at 100 mm, tool bouncing and surface imperfections decrease, which in turn reduces tool vibration and improves cutting performance. However, the bouncing of the tool and the imperfections on the surface of the workpiece grow when the constrained layer damper boring tool is at 150 & 200 mm, which in turn increases tool vibration and degrades the cutting performance.

Table 11.

Optimum input parameters in constrained layer damper.

To minimize	Overhanging length (mm)	Substrate material	Elastic material
Tool vibration	100	Copper	polyurethane
Surface roughness	100	Copper	polyurethane
Tool wear	100	Copper	polyurethane

Table 12.

Evaluation of constrained layer damper tool holder on cutting performance.

Output parameter	Conventional boring bar	Constrained layer damper boring bar	Enhancement(%)
Tool vibration (Displacement - mm)	1.11	0.01412	98
Tool wear (mm)	1.21	0.03	97.5
Surface roughness (µm)	4.08	0.669	83

Table 13.

Evaluation of computational and experimental results.

Output parameter	Computational (Ansys)		Experimental
Output parameter	Conventional boring bar	Constrained layer damper boring bar	Conventional boring bar	Constrained layer damper boring bar
Tool vibration, mm	0.1456	0.14412	1.11	0.01412

The constrained layer damper has a stronger impact on damping than conventional passive dampers. The first is the constrained layer damper boring tool’s overhanging length, which is affected by tool bouncing, and the second is the substrate material, which is influenced by the material’s density and Young’s modulus. Tables 8–10 ANOVA study revealed that, when compared to substrate material and elastic material, overhanging length is the most important factor. The work takes into consideration substrate materials like copper, aluminum, and brass. When compared to aluminum (density 2713 kg/m³ & Young’s modulus 0.7 × 10⁵ MPa) and brass (density 8267 kg/m³ & Young’s modulus 0.9 × 10⁵ MPa), copper (density 8942 kg/m³ & Young’s modulus 1.23 × 10⁵ MPa) offers lower tool vibration, surface roughness, and tool wear. Young’s modulus and material density have an impact on the damping property of the substrate material. The overhanging length is the most important parameter, followed by substrate material and elastic material, according to Tables 8–10 ANOVA study. The work takes into consideration elastic materials including polyurethane, nitrile rubber, and natural rubber. When compared to nitrile rubber (density 75 kg/m³& Young’s modulus 1628 MPa) and natural rubber (density 100 kg/m³ & Young’s modulus 50 MPa), polyurethane (density 1265 kg/m³ & Young’s modulus 1880 MPa) offers decreased tool vibration, surface roughness, and tool wear. Here also the damping property of the elastic material is influenced by the density and Young’s modulus of the material. In constrained layer damping, the vibratory energy from boring bar is transferred to the substrate and elastic materials which are sandwiched. While the Young’s modulus and density of substrate and elastic materials remain high, the vibrating structure’s energy dissipated more efficiently by these materials which gets resulted towards reduction in tool vibration.²⁴ It is also noted that substrate material copper is efficient compared to aluminum and brass because the outer layer copper well sandwiched with boring tool and inner layer of the copper is well sandwiched with elastic material. Once the bouncing of tool (tool vibration) is reduced which in turn reduces the surface irregularities in workpiece and increases the tool life with less noise during the boring process. The computational analysis conducted in this study revealed that the constrained layer damper made of copper and polyurethane exhibited superior damping capabilities when compared to constrained layer damper made of other substrate and elastic materials. The mechanical properties of the constrained layer damper are determined by the combination of the substrate and elastic materials used. In this study, different combinations of copper, brass, and aluminum as substrate materials and polyurethane, nitrile, and natural rubber as elastic materials were tested. The results showed that the combination of copper and polyurethane provided the highest reduction in tool vibration during boring of hardened steel. This superior damping capability of the copper-polyurethane constrained layer damper can be attributed to the mechanical properties of the materials used. Copper material known for conductive and ductile ability provides excellent support to the viscoelastic layer, while polyurethane has excellent damping properties due to its high internal friction and better Young’s modulus. In contrast, the constrained layer damper made of other substrate and elastic materials tested in this study, such as brass, aluminum, nitrile, and natural rubber, exhibited lower damping capabilities. This can be attributed to their lower stiffness, lower damping coefficient, and better Young’s modulus when compared to copper and polyurethane. In summary, the computational analysis conducted in this study showed that the combination of copper and polyurethane provided the best damping capabilities for the constrained layer damper during boring of hardened steel. The results highlight the importance of careful selection of substrate and elastic materials in designing constrained layer damper for effective damping of tool vibration.

Conclusion

In this study, an attempt was made to investigate the effect of the Constrained Layer Damper on the cutting performance of hardened steel during boring process. The study involved designing, developing, and testing of constrained layer damper with varying overhanging length, substrate material, and elastic material to examine the effects of tool wear, surface finish, and tool vibration during boring of hardened AISI4340 steel.

The following inferences were arrived after the detailed study:

• The Constrained Layer Damper demonstrated high effectiveness in reducing tool vibration, resulting in notable improvements in both tool life and surface finish during the boring of hardened AISI4340 steel.

• Computational analysis revealed that the combination of copper as the substrate material and polyurethane as the elastic material provided the most significant reduction in tool vibration. This material combination was identified as the optimal choice for damping purposes.

• Experimental results demonstrated substantial improvements in cutting performance with tool life experienced a remarkable enhancement of approximately 97.5%, surface finish exhibited a substantial improvement of approximately 83% and tool vibration witnessed a remarkable reduction of approximately 98%.

• A meticulous comparison between computational predictions and experimental outcomes indicated a high degree of correlation. This alignment between the two sets of values underscores the accuracy and reliability of the computational method employed for the design and testing of the Constrained Layer Damper.

• The Constrained Layer Damper emerged as an efficient and versatile damping method, showcasing its potential to significantly enhance the cutting performance of boring tools. The quantified improvements in tool life, surface finish, and vibration reduction underscore its practical application and positive impact on machining hardened steel.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Solomon Jenoris Muthiya

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Effect of metallic substrate and rubber elastic materials over passive constrained layer damping on tool vibration during boring process

Abstract

Keywords

Introduction

Computational analysis of boring tool with constrained layer damper—design of constrained layer damper

Experimental analysis

Material and parameters

Design of experiments

Analysis of variance

Result and discussion

Conclusion

Footnotes

Declaration of conflicting interests

Funding

ORCID iD

References