Heinrich Hencky

Heinrich Hencky was the son of a Bavarian treasury civil servant and completed his structural engineering studies at Munich TH in 1908. Following military service, Hencky worked on civil engineering and structural steelwork projects for the local authorities before becoming scientific assistant for theory of structures and bridge-building at Darmstadt TH for the two years prior to World War 1. It was while he was at Darmstadt TH that he was awarded a doctorate for his work on the theory of rectangular plates [Hencky, 1913]. He expanded his dissertation, which was conferred a “distinction”, to cover the theory of circular plates [Hencky, 1915]. He was given a senior management post in a reinforced concrete company in Kharkov in 1914. Following the outbreak of World War 1, Hencky was interned somewhere in the Ural Mountains (1915–18); this is where he met his future wife, Alexandra Yuditskaya. In the spring of 1918, Hencky was able to escape via Kharkov and return to Munich; his wife later followed him. After a short period working as an engineer in the materials testing department of the seaplane trials unit in Warnemünde, he wrote his habilitation thesis on structural mechanics at Darmstadt TH [Hencky, 1920], where he gained a post in the mechanical engineering department on the recommendation of Prof. Ludwig Föppl from Dresden TH. He then worked as a lecturer for applied mechanics at Delft TH from 1922 to 1929, where professors J. M. Burger and C. B. Biezeno were on the teaching and research staff. Hencky's years of creativity in Delft are characterised by his fundamental work on plastic theory [Hencky, 1923] and rheology [Hencky, 1925 & 1929], work which shows Biezeno's influence. His strength hypothesis [Hencky, 1923] was very important for modern structural mechanics. This pioneering work can be placed alongside the strength hypotheses of H. Tresca [Tresca, 1964], M. T. Huber [Huber, 1904/1] and R. v. Mises [Mises, 1913]. Nevertheless, during his time at Delft TH he did not manage to attain the post of professor – his original intention – because he was more a researcher than a teacher; apart from that, the “chemistry” between Hencky and Biezeno was not right. At the invitation of the MIT president at that time, S. Stratton, Hencky was appointed associate professor of mechanics in the MIT's department of mechanical engineering (1930–33). It was there that he supervised the dissertations Yield conditioning of plates and shells by Mises-Hencky Criterion (1931) by Theodore H. H. Pian and Stress field of a plate reinforced by a longitudinal guide and subject to tension (1932) by Robert Conrad. After Stratton's death in 1932, Hencky worked as a consulting engineer in Lisbon (New Hampshire). He was therefore pleased to except Galerkin's offer to take over the chair of applied mechanics at the Chemistry & Technology Institute in Kharkov in 1936. Despite good working conditions, Hencky became the victim of the deteriorating political situation between the USSR and Hitler's Germany. The authorities cancelled his work permit at the end of 1937 and he and his family were instructed to leave the USSR within 24 hours. Supported by the director of MAN, Richard Reinhardt, Hencky began work as a structural engineer responsible for special projects at MAN's Gustavsburg Works (Mainz) on 1 January 1938. The local SS authority mistrusted Hencky and demanded that he not have access to secret documents. However, Reinhardt was able to neutralise this dangerous situation. Therefore, Hencky, protected by Reinhardt, was able to rise to the post of senior engineer at MAN (1941) and was also given responsibility for the materials testing department of the Gustavsburg Works. Only a fragment of his 1943 work Neuere Verfahren der Festigkeitslehre was able to be published [Hencky, 1951] because the original manuscript sent to the Oldenbourg Verlag in Munich was destroyed in an air raid. Hencky retired from MAN at the end of 1950, but just 18 months later he died in an accident in the Alps while pursuing his favourite pastime of mountain climbing.

Main contributions to structural analysis:

• Über den Spannungszustand in rechteckigen ebenen Platten bei gleichmäsig verteilter und bei konzentrierter Belastung [1913];
• Über den Spannungszustand in kreisrunden Platten mit verschwindender Biegesteifigkeit [1915];
• Über die angenäherte Lösung von Stabilitätsproblemen im Raum mittels der elastischen Gelenkkette [1920];
• Kippsicherheit und Achterbildung an angeschlossenen Kreisringen [1921];
• Stabilitätsprobleme der Elastizitätstheorie [1922];
• Über einige statisch bestimmte Fälle des Gleichgewichts in plastischen Körpern [1923];
• Zur Theorie plastischer Deformationen und der hierdurch im Material hervorgerufenen Nachspannungen [1924];
• Die Bewegungsgleichungen beim nichtstationären Fliessen plastischer Massen [1925];
• Das Superpositionsgesetz eines endlich deformierten relaxationsfähigen elastischen Kontinuums und seine Bedeutung für eine exakte Ableitung der Gleichungen für zähe Flüssigkeit in der Eulerschen Form [1929];
• Über die Berücksichtigung der Schubverzerrung in ebenen Platten [1947];
• Neuere Verfahren in der Festigkeitslehre [1951]

Source: Kurrer, Karl-Eugen The History of the Theory of Structures, Wilhelm Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH, Berlin (Deutschland), ISBN 3-433-01838-3, 2008; p. 736