Metallurgy Commons^™

Hydrogen Embrittlement In Shot-Peened Steel, Jia-Huei Tien, David R. Johnson, David Bahr

15th International Conference on Shot Peening

This work investigates the role of shot peening on hydrogen embrittlement resistance in quenched and tempered 1070 steel. Thermal desorption spectroscopy results revealed that shot-peened specimens contained nearly twice the hydrogen (H) content of unpeened samples when charged under the same electrochemical conditions, suggesting the introduction of additional trapping sites occur during peening. The mechanism underlying this behavior can be associated with increased dislocation density and is more consistent with the HELP mechanism. Residual stress measurements show a significant relaxation of compressive stresses in shot-peened specimen after H charging, indicating H enhanced dislocation rearrangement. Both unpeened and peened specimens exhibited …

Anisotropic Residual Stress Measurements In Additively Manufactured 316 Stainless Steel Parts, Rajeshree Varma, Donovan Stumpf, Paul R. Mort

15th International Conference on Shot Peening

Additive manufacturing (AM) using laser powder bed fusion (L-PBF) is increasingly used to produce complex parts for industries like aerospace and medical devices. The intrinsic characteristics of AM – layer-wise deposition and rapid thermal cycling – generate significant, anisotropic, residual stresses that can compromise part quality and performance. Recent studies highlight how these stresses are strongly influenced by process parameters and build orientation. X-ray diffraction (XRD) techniques, including sin²ψ and advanced two-dimensional approaches, have become the preferred methods for non-destructive, directionally resolved measurement of residual stress in AM metals. This review surveys advancements in XRD residual stress methods with a …

From Strain To Stress: Stress Map Testing Of Almen Strips, Donovan Stumpf, Rajeshree Varma, Paul R. Mort

15th International Conference on Shot Peening

Almen strips have long been used to evaluate shot peening intensity, with arc height serving as a proxy for compressive residual stress. Stress mapping tests (SMT) in this work involve the controlled flattening of an Almen test strip onto a spatial pressure sensor, acting as an inferential measurement for the net bending moment caused by the relaxation of the peened strip. This work explores how stress mapping tests add insight into the stress state of Almen strips, potentially offering a fast and practical alternative to residual stress depth profiling. SMT data analysis provides a framework for relating Almen gauge height …

Fourier Analyses Of Optical Profilometry As An Inferential Measurement For Impact Coverage., Langdon Feltner, Paul Mort

15th International Conference on Shot Peening

A critical consideration in peening process design is achieving sufficient impact coverage. Conventional methods for assessing coverage rely on manual inspection, which is time-consuming and poorly suited for automated control. In this work, we investigate the use of frequency-domain analysis to quantify surface modification in peened samples using optical profilometry (OP) data. Three-dimensional surface maps of Almen strips were acquired using a high-resolution OP system and analyzed via fast Fourier transform (FFT) to compute spatial power spectral densities (PSDs). PSD maps and radially averaged profiles reveal consistent amplification of harmonic components similar to the nominal particle size, with increasing intensity …

Improvement Of The Fatigue Behaviour Of Additive Manufatured Scalmalloy By Using Surface Improvement Processes, Francisco José Boby Alcaide, Irene Eras, José Manuel De Los Santos, Alejandro Munoz Castro, Antonio Perinan Butrón, Jorge Sogorb

15th International Conference on Shot Peening

The use of light metals such as Aluminum alloys has experienced a remarkable increase for the additive manufacturing (AM) industry, especially in aerospace.

AM Scalmalloy®. (an Al-Mg-Sc alloy) shows outstanding behavior with much higher mechanical performance with respect to other alloys for powder bed fusion laser-based (PBF-LB) process like AlSi10Mg or AlSi7Mg. Recent studies have mainly focused on static loading, with minor attention to cyclic loading despite its vital importance in many applications.

In this work, the fatigue performance of PBF-LB Scalmalloy was investigated considering the effects of surface treatments to identify the set of optimal post-processes. Shot peening with …

Influence On Shot Peening And Blast Polishing For Rotating Bending Fatigue Strength Of Vacuum Carburized Steel With Circumferential Notch, Yuji Kobayashi, Hayato Taniguchi, Kiyotaka Masaki

15th International Conference on Shot Peening

In order to improve fuel efficiency in automobiles, weight reduction is necessary as well as improving engine efficiency. For transmission gears, thickness reduction is necessary for weight reduction. When the thickness is reduced, the cross-sectional area becomes smaller, and the load stress increases. Therefore, higher fatigue strength is required. Most gears carry out carburizing. Shot peening is often used to improve the fatigue strength of carburized heat-treated parts. After shot peening, compressive residual stress is introduced, but at the same time, surface roughness is increased. Therefore, the processing conditions of shot peening are very important. Blast polishing is a processing …

Reduced Order Approach For Peening Stress Field Variability, Langdon Feltner, Paul Mort

15th International Conference on Shot Peening

A common goal in shot peening research is to connect operational parameters to resultant residual stress fields, providing a means to control and optimize the effectiveness of surface treatment. In practice, experimental measurements of residual stresses are often averaged values over regions that are large in comparison to an impact dimple. In fact, the stochastic nature of impact locations leads to residual stress fields that are distributed. Finite element peening simulations confirm this observation. The goal of this report is to connect operational parameters to localized fluctuations in residual stress through probabilistic reasoning (Figure 1). In particular, the development of …

The Effect Of Surface Treatment On The Fatigue Strength Of Sus316l Additive Manufactured Products, Hitoshi Nishijima, Yuji Kobayashi, Toshiya Tsuji, Kiyotaka Masaki

15th International Conference on Shot Peening

Rotating bending fatigue tests were conducted to investigate the effect of shot peening and barrel finishing on fatigue properties of SUS316L made by laser PBF which was one of additive manufacturing processes. Surface roughness, residual stress, and fatigue strength were investigated for each specimen. As a result, the fatigue strength of the barrel finished specimens was almost same or better than that of the shot peened specimens. Barrel finished specimens increased 4.1 times higher fatigue strength than as-built specimens. The surface roughness of the specimens after barrel finishing was reduced by up to 96% compared to the as-built specimens. On …

Dynamic Flowsheet Modeling Of Shot Peening Processes, Langdon Feltner, Paul Mort

15th International Conference on Shot Peening

Process flowsheet modeling is used to map and predict performance by integrating sub-models within a system. This paper presents a dynamic flowsheet for shot peening used to track the effects of media characteristics, removal of worn media, and replenishment thereof. Input parameters include media characteristics, media feed rate, velocity (i.e., air pressure), effective impact area (i.e., nozzle setup), and recharge replenishment. The media working mix is described dynamically using tri-modal size and shape characteristics: as-manufactured, conditioned, and worn modes, each having impact-dependent rate coefficients for transition to the next mode, i.e., as-manufactured > conditioned > worn > debris. The flowsheet includes the effect …

Evaluating The Effectiveness Of Localized Masking To Prevent Changes In Residual Stress When Shot Peening, James R. Harrison, James Pineault, Tom Mills

15th International Conference on Shot Peening

When shot peening components, it is common practice to mask certain localized regions where peening roughness is not desirable. For example, surfaces that have been highly machined such as bearing races or areas of interference-fit may require masking to protect them from the cold working effects of shot peening. Oftentimes shot peening the grip sections of fatigue test coupons can prevent cracking and failures due to fretting fatigue in the grip area but could affect the outcome of the test if applied to the gauge section of the coupons. Thus, maintaining an “as machined” surface roughness is the most common …

Improving Fatigue Strength And Life Of Single Crystal Cmsx-4, Jochen Peter Fuhr, Lloyd Hackel, Nicolau I. Morar, Noah Holtham, Keivan Davami, Montu Sharma, Rajkumar Roy

15th International Conference on Shot Peening

The deep penetration of laser peening (LP) and retention of residual stress at high temperature by LP is significant in improving fatigue life and strength of superalloys exposed to high temperature and corrosion. Single crystal CMSX-4, was evaluated for stress relaxation and both fatigue life and fatigue strength of material that was LP-treated compared to non-LP and shot-peened (SP) specimens. LP was done with multiple layers using a 20 J/pulse laser where the laser high energy enabled using a 5 mm spot size on the metal surface. Stress measurements by the slitting technique showed the plastic penetration depth exceeded SP …