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Title: Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds (2006-01-0531)

Abstract

This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t1/2 can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
921408
Report Number(s):
PNNL-SA-55842
VT0502010; TRN: US200804%%801
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: SAE Transactions. Journal of Materials & Manufacturing, 115(Part 5):509-516; Journal Volume: 115; Journal Issue: Part 5
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CROSS SECTIONS; ENERGY ABSORPTION; FRACTURES; PEAK LOAD; PERFORMANCE; STATISTICAL DATA; STEELS; WELDED JOINTS; Advanced high strength steels; Spot Welds; Weld Fusion Zone Size; Weld Failure Mode

Citation Formats

Sun, Xin, Stephens, Elizabeth V., and Khaleel, Mohammad A.. Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds (2006-01-0531). United States: N. p., 2007. Web.
Sun, Xin, Stephens, Elizabeth V., & Khaleel, Mohammad A.. Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds (2006-01-0531). United States.
Sun, Xin, Stephens, Elizabeth V., and Khaleel, Mohammad A.. Thu . "Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds (2006-01-0531)". United States. doi:.
@article{osti_921408,
title = {Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds (2006-01-0531)},
author = {Sun, Xin and Stephens, Elizabeth V. and Khaleel, Mohammad A.},
abstractNote = {This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t1/2 can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.},
doi = {},
journal = {SAE Transactions. Journal of Materials & Manufacturing, 115(Part 5):509-516},
number = Part 5,
volume = 115,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on themore » joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.« less
  • This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using limit load based analytical model and micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populationsmore » with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 materials examined. The critical fusion zone size for nugget pullout shall be derived for individual materials based on different base metal properties as well as different heat affected zone (HAZ) and weld properties resulted from different welding parameters.« less
  • This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS) under lap shear loading condition. DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. Static weld strength tests using lap shear samples were performed on the joint populations with various fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statisticalmore » data analysis tools. The results in this study show that AHSS spot welds with conventionally required fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 welds under lap shear loading. Moreover, failure mode has strong influence on weld peak load and energy absorption for all the DP800 welds and the TRIP800 small welds: welds failed in pullout mode have statistically higher strength and energy absorption than those failed in interfacial fracture mode. For TRIP800 welds above the critical fusion zone level, the influence of weld failure modes on peak load and energy absorption diminishes. Scatter plots of peak load and energy absorption versus weld fusion zone size were then constructed, and the results indicate that fusion zone size is the most critical factor in weld quality in terms of peak load and energy absorption for both DP800 and TRIP800 spot welds.« less
  • This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of aluminum spot welded samples using a combined experimental, statistical and analytical approach. Static strength tests using coupon configurations of lap shear, cross tension and coach peel were performed on joint populations with a controlled fusion zone size. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical models. An analytical model was developed to determine the failure mode of an aluminum resistance spot weld based on limit load analyses. It was found that fusion zonemore » size, sheet thickness, and the level and location of weld porosity/defects are the main factors influencing the cross-tension failure mode of an aluminum spot weld.« less
  • This paper examines the effects of failure modes on the static strength and total energy absorption of aluminum spot-welded samples using experimental, statistical, and analytical approaches. The main failure modes for aluminum spot welds are nugget pullout and interfacial fracture. Two populations of aluminum spot welds were studied. Within each population, coupon configurations of lap shear, cross tension and coach peel were considered. Thirty replicate static strength tests were performed for each coupon configuration. The resulted peak load and energy absorption level associated with each failure mode was studied using statistical models. Next, an analytical model was developed to determinemore » the failure mode of an aluminum resistance spot weld based on stress analysis. It is found that weld size, sheet thickness, and level of weld porosity and defects are the main factors determining the cross tension failure mode for an aluminum spot weld. The peak load and energy absorption levels for the cross tension and coach peel samples tested are found not to be very sensitive to the failure modes under static loading.« less