ASTM B851-04(R2020) pdf free download

ASTM B851-04(R2020) pdf free download.Standard Specification for Automated Controlled Shot Peening of Metallic Articles Prior to Nickel, Autocatalytic Nickel, or Chromium Plating, or as Final Finish
1. Scope
1.1 This specification covers the requirements for automated, controlled shot peening of metallic articles prior to electrolytic or autocatalytic deposition of nickel or chromium, or as a final finish, using shot made of cast steel, conditioned cut wire, or ceramic media. The process is applicable to those materials on which test work has shown it to be beneficial within given intensity ranges. It is not suitable for brittle materials. Hand peening and rotary flap peening are excluded specifically. 1.2 Shot peening induces residual compressive stresses in the surface and near-surface layers of metallic articles, control- ling or limiting the reduction in fatigue properties that occurs from nickel or chromium plating of the article, or the fatigue properties of unplated articles. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions: 3.1.1 Almen strip—UNS G10700 carbon steel specimens that are used to calibrate the energy of a shot peening stream (see Fig. 1). 3.1.2 Almen strip holding fixture—a fixture for holding Almen strips in suitable locations that represent the position and angular orientation ofthe surfaces ofa part where intensity is to be determined and verified (see Fig. 2). 3.1.3 arc height—flat Almen strips, when subjected to a stream of shot moving at an adequate velocity, bending in an arc corresponding to the amount of energy transmitted by the shot stream. The height of the curved arc measured in millimeters is the arc height, measured by an Almen gage (see Fig. 3). 3.1.4 automatic equipment—shot peening equipment in which parts, fixtures, nozzles, and peening parameters are preset by hand or by locating fixtures and verified by inspection personnel. The peening time is monitored automatically, and the air pressure or wheel speed is set manually. 3.1.5 compressive stresses—cold working or stretching the surface beyond the elastic limit by shot peening, creating a layer in compression below the surface. The depth of compres- sive stresses is measured by the crown of the dimple to the depth. 3.1.6 coverage—the extent of obliteration of the original surface by dimples produced by impact from individual shot particles and expressed as a percentage. See Note 1. 3.1.7 depth ofcompressive stresses—where the stress profile passes through 0 stress. 3.1.8 intensity—the Almen strip arc height at saturation. Arc height is not termed intensity correctly unless saturation is achieved. 3.1.9 liquid tracer system—a liquid coating material bearing a pigment that fluoresces under an ultraviolet light and removes at a rate proportioned to peening coverage. 3.1.10 microprocessor-controlled equipment—peening equipment that has nozzle holding fixtures and is computer controlled for processing, monitoring, and documentation of the peening parameters critical to process certification.
3.1.11 nozzle holding fixture—a fixture that holds the nozzles at the required location, distance, and angle in a locked position during the peening operation. 3.1.12 process interrupt parameters—for critical peening operations, parameters such as shot flow, air pressure, part r/min, oscillation rate, and cycle time that must be monitored within process requirements. 3.1.13 saturation—the minimum duration of peening nec- essary to achieve the desired Almen intensity which, when doubled, does not increase the Almen strip arc height by more than 10 %. 3.1.14 saturation curve—a curve that plots peening time on the Almen strip (abscissa) versus Almen strip arc height (ordinate) achieved for the peening time (see Fig. 4). 3.1.15 surface obliteration—the condition of a peened sur- face in which 100 % of the surface has been dimpled with shot impressions.