Design of a Tribo-Simulator for Investigation of the Tribological Behavior of Stainless-Steel Sheets Under Different Contact Conditions

Luiz, Valmir Dias; Rodrigues, Paulo César de Matos

doi:10.1590/1980-5373-MR-2021-0220

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Articles • Mat. Res. 25 • 2022 • https://doi.org/10.1590/1980-5373-MR-2021-0220 copy

Design of a Tribo-Simulator for Investigation of the Tribological Behavior of Stainless-Steel Sheets Under Different Contact Conditions

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

In sheet metal forming (SMF), deformation is caused by the relative movement between the sheet and tool, which generates friction forces. However, materials behave differently during plastic deformation. In this study, a tribo-simulator was designed to investigate the effect of different contact conditions or formability tests on the tribological behavior of AISI 304 and AISI 430 stainless-steel sheets. The effects of the texture and microstructure of the sheets on the measured coefficients of friction (COFs) and changes that occurred on the tribosurfaces also were investigated. Roughness and microhardness measurements, optical and scanning electron microscopy, and X-ray diffraction were used in the analyses. The tribo-simulator was successfully manufactured, and the repeatability of the measured COFs was satisfactory (standard deviation of ~0.02). A comparative analysis of the formability tests revealed differences in the COFs. In the bending under tension test, the COF for ferritic steel was 33% higher, while in the strip-tension test, the COF for austenitic steel was 44% higher. Friction was strongly influenced by the texture and microstructural characteristics of the steel sheets. The samples exhibited galling due to severe adhesive wear.

Keywords:
Sheet metal forming; AISI 304 and AISI 430 stainless-steel sheets; Tribo-simulator; Formability tests; Coefficients of friction

Initials	Operational parameters	Description
F₁ e F₂	Applied forces (max.)	44.5 kN
T	Torque at the bending pin (max.)	50 Nm
l	Metal strip length	530 to 770 mm
w	Metal strip width	25 to 30 mm
R	Bending pin radius	6.5 mm
θ	Bending angle	90^o
V₁ e V₂	Drawing speed (max.)*	73 mm/s^* * the speed of the hydraulic actuators is adjusted using in-line flow valves. Reference: Paper authors.
P	Hydraulic unit pressure (max.)	250 bar
W	Electric motor power	10 HP
Q	Pumps flow	1.4 lpm and 14 lpm
C	Reservoir capacity (max.)	50 lt
d₁	Piston diameter	63 mm
d₂	Piston rod diameter	25.4 mm
h	Cylinder displacement (max.)	250 mm

Design phases	List of materials	Cost
Hydraulic system	Hydraulic unit, hydraulic cylinders, and filtered oil	USD 6247.13
Assembly structure	Central column and side support bases (I-profile), support bases of the hydraulic cylinders (laminated steel U-profile), and support bases of the displacement and proximity sensors (L-profile)	USD 478.11
Pieces and accessories	Die and bending pins, grip claws, and assembly accessories of the torque sensor	USD 318.11
Data acquisition system (DAS)	Load cell (RAS1-10KS-S, 44.5 kN, and 0.02% precision), LVDT sensors (KTM series, 275 mm, accuracy of 0.05%), torque sensor (ZHKY8050A, 50 Nm, 0.1% accuracy), torque meter (PY801, 0.2% accuracy), resistive interfaces (0.02% accuracy, 24-bit analog–digital converter, 500 Hz), and application software (SensorVUE, Loadstar Sensors)	USD 8669.17
Automation system	Standard box with electrical parts and devices (circuit breaker, connection terminals, relays, power supply, etc.), programmable logic controller (PLC) (Delta 20SX2), human–machine interface (HMI) (Delta 4.3” DOP-B03S211), and operational software development	USD 3098.68
Total cost		USD 18,811.20

Material	C	Mn	Si	Cr	Ni	Mo	Nb	N (ppm)
AISI 304	0.0218	1.0579	0.2689	18.2293	8.1220	0.0831	0.0042	206
AISI 430	0.0164	0.2454	0.2447	16.4810	0.2964	0.0234	0.3384	231

Material	Sample direction	$S_{y}$ (MPa)	$S_{u}$ (MPa)	$e_{u}$ (%)	$e_{t}$ (%)	n	$R$	$\bar{R}$	$Δ R$
AISI 304	0°	276.8	605.2	64.2	70.7	0.433	0.876	1.076	-0.393
	45°	276.6	590.0	63.9	71.3	0.422	1.272
	90°	281.2	603.8	63.7	71.2	0.434	0.882
AISI 430	0°	316.1	464.9	22.3	32.7	0.205	1.419	1.366	0.340
	45°	343.4	475.6	17.9	27.2	0.188	1.196
	90°	317.5	466.5	19.8	33.2	0.201	1.654

Material	Surface roughness parameters (µm)
Material	R_a	R_q	R_z	R_t
AISI 304	0.071±0.006	0.077±0.012	0.902±0.119	1.217±0.203
AISI 430	0.048±0.007	0.068±0.015	0.691±0.273	1.349±0.995
Bending pins^* * two bending pins were manufactured and the values listed refers to the average of their roughness parameters. Ra = average roughness, Rq = root mean square roughness parameter, Rz = zero-point peak-valley surface roughness, Rt = total height. Reference: Paper authors. Analysis performed during this research.	0.539±0.025	0.737±0.044	4.527±0.396	6.175±0.836

Parameter	Description
Specimen direction	0° and 90°
Specimen dimensions	0.8 × 25 × 750 mm
Speed drawing	10 mm/s
Pins radius	6.5 mm

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[1] *e-mail: valmir@cefetmg.br